How to write Neumann and mixed conditions in Freefem++?

General Discussion
1

I am not sure whether this question is addressed earlier or not.
Actually i want to know how shall i write the Neumann and Mixed boundary conditions in Freefem++?

T.I.A

2

This depend of you problem and of the method use to get the approximation.

you can see
https://doc.freefem.org/documentation/finite-element.html#problem-definition